Aile (アイル, Airu?) is Emperor Mateus's mother. While she doesn't appear in Final Fantasy II proper, she has a role in its Japan exclusive novelization Final Fantasy II Muma no Meikyū. Aile was initially included in the design documents of the game as a fortune-teller who would help Firion and his party out when the player lost track of their current objective.
Palamecia is cursed with demonic influences that corrupt its emperors. Satan, desiring to rule the world by human proxy, turns men into malicious masterminds by using everything at its disposal to pollute their thoughts with its malice. Satan originates from the beginning of the world when it became trapped within the indestructible "Stone of Iludia" and swore revenge by any means.
After ascending to the throne, Mateus exiles Aile to the deserts of Palamecia, and yet she still spends her life trying to find a way to save him. Aile and Minwu team up to find a crystal, which can purify the land. It ends up being too late to save Mateus, but it helps to bring peace to the world.
Aile is French for "wing."